1. Field of the Invention
The present invention relates to a display control apparatus for a vehicle which is used to control a display operation of a display member after a vehicle key switch is switched off, particularly to the display control apparatus for maintaining a nightly diminished brightness for a predetermined time period even if it is switched to a daylight brightness condition.
2. Description of the Related Art
Recently, in an interior of a vehicle, to display meters and various kinds of information, there is often used a display member such as a liquid crystal panel, or a liquid crystal display panel or a fluorescent display panel using a backlight. This display member is generally linked with a vehicle key switch and is set in the following manner: that is, when the vehicle key switch is switched on (ON), the display member can be operated for display and, when the vehicle key switch is switched off (OFF), it stops its operation for display (display operation).
But, in case where, when the vehicle key switch is switched off, the display operation of the display member is stopped immediately, there arises an inconvenience that, after the vehicle key switch is switched off, display contents cannot clearly be seen. In order to avoid this, there is proposed a display control apparatus which, using a delay timer, can maintain the display operation for a predetermined time period after the vehicle key switch is switched off.
However, in the case where a set time of the delay timer is set long, not only a battery is forced to bear an unnecessary load but also, when a driver leaves the vehicle, the display member still continues to display the display contents, thereby causing the driver to have a fear that the battery is exhausted; and, therefore, the driver must stay in the vehicle until he or she makes certain that the display operation is completely stopped. In order to avoid this, the inventors of the present patent application have developed the display control apparatus for the vehicle which, after the vehicle key switch is switched off, can continue its necessary minimum display operation and also can provide good visual confirmation without exhausting unnecessarily, and have previously filed a similar patent application for the present display control apparatus for the vehicle (Patent Application No. 2000-197834).
By the way, there exists the vehicle of the type that, headlights can be turned off even when a headlight switch is switched on after a vehicle key switch is switched off in order to prevent the driver from forgetting to turn off the headlights. Also, in the vehicle of this type, there is included the vehicle which can use two kinds of illumination brightness respectively for daytime and nighttime in order to enhance a visibility of the display contents of the above-mentioned display member such as the liquid crystal panel. That is, for this kind of vehicle, when the headlights are on, the time is judged as a nighttime and thus, as the illumination brightness of the display member, there is used nighttime reduced brightness. When the headlights are off, the time is judged as a daytime and thus, as the illumination brightness of the display member, there is used a daytime brightness.
Therefore, in the above-mentioned vehicle, in case where the headlights are turned off by switching off the vehicle key switch, even when the headlight switch is switched on, the time is judged to be the daytime and thus, as the illumination brightness of the display member, there is used the daytime brightness. As a result of this, the illumination brightness of the display member within a delay time set by a delay timer is switched from the nighttime reduced brightness to the daytime brightness, thereby dazzling the driver. Also, since the daytime brightness is used as the illumination brightness during the nighttime, the battery is consumed unnecessarily.